/*
 * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package java.util;

import java.nio.file.Path;
import java.nio.file.Files;
import java.util.regex.*;
import java.io.*;
import java.math.*;
import java.nio.*;
import java.nio.channels.*;
import java.nio.charset.*;
import java.text.*;
import java.util.Locale;

import sun.misc.LRUCache;

/**
 * A simple text scanner which can parse primitive types and strings using
 * regular expressions.
 *
 * <p>A <code>Scanner</code> breaks its input into tokens using a
 * delimiter pattern, which by default matches whitespace. The resulting
 * tokens may then be converted into values of different types using the
 * various <tt>next</tt> methods.
 *
 * <p>For example, this code allows a user to read a number from
 * <tt>System.in</tt>:
 * <blockquote><pre>{@code
 *     Scanner sc = new Scanner(System.in);
 *     int i = sc.nextInt();
 * }</pre></blockquote>
 *
 * <p>As another example, this code allows <code>long</code> types to be
 * assigned from entries in a file <code>myNumbers</code>:
 * <blockquote><pre>{@code
 *      Scanner sc = new Scanner(new File("myNumbers"));
 *      while (sc.hasNextLong()) {
 *          long aLong = sc.nextLong();
 *      }
 * }</pre></blockquote>
 *
 * <p>The scanner can also use delimiters other than whitespace. This
 * example reads several items in from a string:
 * <blockquote><pre>{@code
 *     String input = "1 fish 2 fish red fish blue fish";
 *     Scanner s = new Scanner(input).useDelimiter("\\s*fish\\s*");
 *     System.out.println(s.nextInt());
 *     System.out.println(s.nextInt());
 *     System.out.println(s.next());
 *     System.out.println(s.next());
 *     s.close();
 * }</pre></blockquote>
 * <p>
 * prints the following output:
 * <blockquote><pre>{@code
 *     1
 *     2
 *     red
 *     blue
 * }</pre></blockquote>
 *
 * <p>The same output can be generated with this code, which uses a regular
 * expression to parse all four tokens at once:
 * <blockquote><pre>{@code
 *     String input = "1 fish 2 fish red fish blue fish";
 *     Scanner s = new Scanner(input);
 *     s.findInLine("(\\d+) fish (\\d+) fish (\\w+) fish (\\w+)");
 *     MatchResult result = s.match();
 *     for (int i=1; i<=result.groupCount(); i++)
 *         System.out.println(result.group(i));
 *     s.close();
 * }</pre></blockquote>
 *
 * <p>The <a name="default-delimiter">default whitespace delimiter</a> used
 * by a scanner is as recognized by {@link java.lang.Character}.{@link
 * java.lang.Character#isWhitespace(char) isWhitespace}. The {@link #reset}
 * method will reset the value of the scanner's delimiter to the default
 * whitespace delimiter regardless of whether it was previously changed.
 *
 * <p>A scanning operation may block waiting for input.
 *
 * <p>The {@link #next} and {@link #hasNext} methods and their
 * primitive-type companion methods (such as {@link #nextInt} and
 * {@link #hasNextInt}) first skip any input that matches the delimiter
 * pattern, and then attempt to return the next token. Both <tt>hasNext</tt>
 * and <tt>next</tt> methods may block waiting for further input.  Whether a
 * <tt>hasNext</tt> method blocks has no connection to whether or not its
 * associated <tt>next</tt> method will block.
 *
 * <p> The {@link #findInLine}, {@link #findWithinHorizon}, and {@link #skip}
 * methods operate independently of the delimiter pattern. These methods will
 * attempt to match the specified pattern with no regard to delimiters in the
 * input and thus can be used in special circumstances where delimiters are
 * not relevant. These methods may block waiting for more input.
 *
 * <p>When a scanner throws an {@link InputMismatchException}, the scanner
 * will not pass the token that caused the exception, so that it may be
 * retrieved or skipped via some other method.
 *
 * <p>Depending upon the type of delimiting pattern, empty tokens may be
 * returned. For example, the pattern <tt>"\\s+"</tt> will return no empty
 * tokens since it matches multiple instances of the delimiter. The delimiting
 * pattern <tt>"\\s"</tt> could return empty tokens since it only passes one
 * space at a time.
 *
 * <p> A scanner can read text from any object which implements the {@link
 * java.lang.Readable} interface.  If an invocation of the underlying
 * readable's {@link java.lang.Readable#read} method throws an {@link
 * java.io.IOException} then the scanner assumes that the end of the input
 * has been reached.  The most recent <tt>IOException</tt> thrown by the
 * underlying readable can be retrieved via the {@link #ioException} method.
 *
 * <p>When a <code>Scanner</code> is closed, it will close its input source
 * if the source implements the {@link java.io.Closeable} interface.
 *
 * <p>A <code>Scanner</code> is not safe for multithreaded use without
 * external synchronization.
 *
 * <p>Unless otherwise mentioned, passing a <code>null</code> parameter into
 * any method of a <code>Scanner</code> will cause a
 * <code>NullPointerException</code> to be thrown.
 *
 * <p>A scanner will default to interpreting numbers as decimal unless a
 * different radix has been set by using the {@link #useRadix} method. The
 * {@link #reset} method will reset the value of the scanner's radix to
 * <code>10</code> regardless of whether it was previously changed.
 *
 * <h3> <a name="localized-numbers">Localized numbers</a> </h3>
 *
 * <p> An instance of this class is capable of scanning numbers in the standard
 * formats as well as in the formats of the scanner's locale. A scanner's
 * <a name="initial-locale">initial locale </a>is the value returned by the {@link
 * java.util.Locale#getDefault(Locale.Category)
 * Locale.getDefault(Locale.Category.FORMAT)} method; it may be changed via the {@link
 * #useLocale} method. The {@link #reset} method will reset the value of the
 * scanner's locale to the initial locale regardless of whether it was
 * previously changed.
 *
 * <p>The localized formats are defined in terms of the following parameters,
 * which for a particular locale are taken from that locale's {@link
 * java.text.DecimalFormat DecimalFormat} object, <tt>df</tt>, and its and
 * {@link java.text.DecimalFormatSymbols DecimalFormatSymbols} object,
 * <tt>dfs</tt>.
 *
 * <blockquote><dl>
 * <dt><i>LocalGroupSeparator&nbsp;&nbsp;</i>
 * <dd>The character used to separate thousands groups,
 * <i>i.e.,</i>&nbsp;<tt>dfs.</tt>{@link
 * java.text.DecimalFormatSymbols#getGroupingSeparator
 * getGroupingSeparator()}
 * <dt><i>LocalDecimalSeparator&nbsp;&nbsp;</i>
 * <dd>The character used for the decimal point,
 * <i>i.e.,</i>&nbsp;<tt>dfs.</tt>{@link
 * java.text.DecimalFormatSymbols#getDecimalSeparator
 * getDecimalSeparator()}
 * <dt><i>LocalPositivePrefix&nbsp;&nbsp;</i>
 * <dd>The string that appears before a positive number (may
 * be empty), <i>i.e.,</i>&nbsp;<tt>df.</tt>{@link
 * java.text.DecimalFormat#getPositivePrefix
 * getPositivePrefix()}
 * <dt><i>LocalPositiveSuffix&nbsp;&nbsp;</i>
 * <dd>The string that appears after a positive number (may be
 * empty), <i>i.e.,</i>&nbsp;<tt>df.</tt>{@link
 * java.text.DecimalFormat#getPositiveSuffix
 * getPositiveSuffix()}
 * <dt><i>LocalNegativePrefix&nbsp;&nbsp;</i>
 * <dd>The string that appears before a negative number (may
 * be empty), <i>i.e.,</i>&nbsp;<tt>df.</tt>{@link
 * java.text.DecimalFormat#getNegativePrefix
 * getNegativePrefix()}
 * <dt><i>LocalNegativeSuffix&nbsp;&nbsp;</i>
 * <dd>The string that appears after a negative number (may be
 * empty), <i>i.e.,</i>&nbsp;<tt>df.</tt>{@link
 * java.text.DecimalFormat#getNegativeSuffix
 * getNegativeSuffix()}
 * <dt><i>LocalNaN&nbsp;&nbsp;</i>
 * <dd>The string that represents not-a-number for
 * floating-point values,
 * <i>i.e.,</i>&nbsp;<tt>dfs.</tt>{@link
 * java.text.DecimalFormatSymbols#getNaN
 * getNaN()}
 * <dt><i>LocalInfinity&nbsp;&nbsp;</i>
 * <dd>The string that represents infinity for floating-point
 * values, <i>i.e.,</i>&nbsp;<tt>dfs.</tt>{@link
 * java.text.DecimalFormatSymbols#getInfinity
 * getInfinity()}
 * </dl></blockquote>
 *
 * <h4> <a name="number-syntax">Number syntax</a> </h4>
 *
 * <p> The strings that can be parsed as numbers by an instance of this class
 * are specified in terms of the following regular-expression grammar, where
 * Rmax is the highest digit in the radix being used (for example, Rmax is 9 in base 10).
 *
 * <dl>
 * <dt><i>NonAsciiDigit</i>:
 * <dd>A non-ASCII character c for which
 * {@link java.lang.Character#isDigit Character.isDigit}<tt>(c)</tt>
 * returns&nbsp;true
 *
 * <dt><i>Non0Digit</i>:
 * <dd><tt>[1-</tt><i>Rmax</i><tt>] | </tt><i>NonASCIIDigit</i>
 *
 * <dt><i>Digit</i>:
 * <dd><tt>[0-</tt><i>Rmax</i><tt>] | </tt><i>NonASCIIDigit</i>
 *
 * <dt><i>GroupedNumeral</i>:
 * <dd><tt>(&nbsp;</tt><i>Non0Digit</i>
 * <i>Digit</i><tt>?
 * </tt><i>Digit</i><tt>?</tt>
 * <dd>&nbsp;&nbsp;&nbsp;&nbsp;<tt>(&nbsp;</tt><i>LocalGroupSeparator</i>
 * <i>Digit</i>
 * <i>Digit</i>
 * <i>Digit</i><tt> )+ )</tt>
 *
 * <dt><i>Numeral</i>:
 * <dd><tt>( ( </tt><i>Digit</i><tt>+ )
 * | </tt><i>GroupedNumeral</i><tt> )</tt>
 *
 * <dt><a name="Integer-regex"><i>Integer</i>:</a>
 * <dd><tt>( [-+]? ( </tt><i>Numeral</i><tt>
 * ) )</tt>
 * <dd><tt>| </tt><i>LocalPositivePrefix</i> <i>Numeral</i>
 * <i>LocalPositiveSuffix</i>
 * <dd><tt>| </tt><i>LocalNegativePrefix</i> <i>Numeral</i>
 * <i>LocalNegativeSuffix</i>
 *
 * <dt><i>DecimalNumeral</i>:
 * <dd><i>Numeral</i>
 * <dd><tt>| </tt><i>Numeral</i>
 * <i>LocalDecimalSeparator</i>
 * <i>Digit</i><tt>*</tt>
 * <dd><tt>| </tt><i>LocalDecimalSeparator</i>
 * <i>Digit</i><tt>+</tt>
 *
 * <dt><i>Exponent</i>:
 * <dd><tt>( [eE] [+-]? </tt><i>Digit</i><tt>+ )</tt>
 *
 * <dt><a name="Decimal-regex"><i>Decimal</i>:</a>
 * <dd><tt>( [-+]? </tt><i>DecimalNumeral</i>
 * <i>Exponent</i><tt>? )</tt>
 * <dd><tt>| </tt><i>LocalPositivePrefix</i>
 * <i>DecimalNumeral</i>
 * <i>LocalPositiveSuffix</i>
 * <i>Exponent</i><tt>?</tt>
 * <dd><tt>| </tt><i>LocalNegativePrefix</i>
 * <i>DecimalNumeral</i>
 * <i>LocalNegativeSuffix</i>
 * <i>Exponent</i><tt>?</tt>
 *
 * <dt><i>HexFloat</i>:
 * <dd><tt>[-+]? 0[xX][0-9a-fA-F]*\.[0-9a-fA-F]+
 * ([pP][-+]?[0-9]+)?</tt>
 *
 * <dt><i>NonNumber</i>:
 * <dd><tt>NaN
 * | </tt><i>LocalNan</i><tt>
 * | Infinity
 * | </tt><i>LocalInfinity</i>
 *
 * <dt><i>SignedNonNumber</i>:
 * <dd><tt>( [-+]? </tt><i>NonNumber</i><tt> )</tt>
 * <dd><tt>| </tt><i>LocalPositivePrefix</i>
 * <i>NonNumber</i>
 * <i>LocalPositiveSuffix</i>
 * <dd><tt>| </tt><i>LocalNegativePrefix</i>
 * <i>NonNumber</i>
 * <i>LocalNegativeSuffix</i>
 *
 * <dt><a name="Float-regex"><i>Float</i></a>:
 * <dd><i>Decimal</i>
 * <tt>| </tt><i>HexFloat</i>
 * <tt>| </tt><i>SignedNonNumber</i>
 *
 * </dl>
 * <p>Whitespace is not significant in the above regular expressions.
 *
 * @since 1.5
 */
public final class Scanner implements Iterator<String>, Closeable {

  // Internal buffer used to hold input
  private CharBuffer buf;

  // Size of internal character buffer
  private static final int BUFFER_SIZE = 1024; // change to 1024;

  // The index into the buffer currently held by the Scanner
  private int position;

  // Internal matcher used for finding delimiters
  private Matcher matcher;

  // Pattern used to delimit tokens
  private Pattern delimPattern;

  // Pattern found in last hasNext operation
  private Pattern hasNextPattern;

  // Position after last hasNext operation
  private int hasNextPosition;

  // Result after last hasNext operation
  private String hasNextResult;

  // The input source
  private Readable source;

  // Boolean is true if source is done
  private boolean sourceClosed = false;

  // Boolean indicating more input is required
  private boolean needInput = false;

  // Boolean indicating if a delim has been skipped this operation
  private boolean skipped = false;

  // A store of a position that the scanner may fall back to
  private int savedScannerPosition = -1;

  // A cache of the last primitive type scanned
  private Object typeCache = null;

  // Boolean indicating if a match result is available
  private boolean matchValid = false;

  // Boolean indicating if this scanner has been closed
  private boolean closed = false;

  // The current radix used by this scanner
  private int radix = 10;

  // The default radix for this scanner
  private int defaultRadix = 10;

  // The locale used by this scanner
  private Locale locale = null;

  // A cache of the last few recently used Patterns
  private LRUCache<String, Pattern> patternCache =
      new LRUCache<String, Pattern>(7) {
        protected Pattern create(String s) {
          return Pattern.compile(s);
        }

        protected boolean hasName(Pattern p, String s) {
          return p.pattern().equals(s);
        }
      };

  // A holder of the last IOException encountered
  private IOException lastException;

  // A pattern for java whitespace
  private static Pattern WHITESPACE_PATTERN = Pattern.compile(
      "\\p{javaWhitespace}+");

  // A pattern for any token
  private static Pattern FIND_ANY_PATTERN = Pattern.compile("(?s).*");

  // A pattern for non-ASCII digits
  private static Pattern NON_ASCII_DIGIT = Pattern.compile(
      "[\\p{javaDigit}&&[^0-9]]");

  // Fields and methods to support scanning primitive types

  /**
   * Locale dependent values used to scan numbers
   */
  private String groupSeparator = "\\,";
  private String decimalSeparator = "\\.";
  private String nanString = "NaN";
  private String infinityString = "Infinity";
  private String positivePrefix = "";
  private String negativePrefix = "\\-";
  private String positiveSuffix = "";
  private String negativeSuffix = "";

  /**
   * Fields and an accessor method to match booleans
   */
  private static volatile Pattern boolPattern;
  private static final String BOOLEAN_PATTERN = "true|false";

  private static Pattern boolPattern() {
    Pattern bp = boolPattern;
    if (bp == null) {
      boolPattern = bp = Pattern.compile(BOOLEAN_PATTERN,
          Pattern.CASE_INSENSITIVE);
    }
    return bp;
  }

  /**
   * Fields and methods to match bytes, shorts, ints, and longs
   */
  private Pattern integerPattern;
  private String digits = "0123456789abcdefghijklmnopqrstuvwxyz";
  private String non0Digit = "[\\p{javaDigit}&&[^0]]";
  private int SIMPLE_GROUP_INDEX = 5;

  private String buildIntegerPatternString() {
    String radixDigits = digits.substring(0, radix);
    // \\p{javaDigit} is not guaranteed to be appropriate
    // here but what can we do? The final authority will be
    // whatever parse method is invoked, so ultimately the
    // Scanner will do the right thing
    String digit = "((?i)[" + radixDigits + "]|\\p{javaDigit})";
    String groupedNumeral = "(" + non0Digit + digit + "?" + digit + "?(" +
        groupSeparator + digit + digit + digit + ")+)";
    // digit++ is the possessive form which is necessary for reducing
    // backtracking that would otherwise cause unacceptable performance
    String numeral = "((" + digit + "++)|" + groupedNumeral + ")";
    String javaStyleInteger = "([-+]?(" + numeral + "))";
    String negativeInteger = negativePrefix + numeral + negativeSuffix;
    String positiveInteger = positivePrefix + numeral + positiveSuffix;
    return "(" + javaStyleInteger + ")|(" +
        positiveInteger + ")|(" +
        negativeInteger + ")";
  }

  private Pattern integerPattern() {
    if (integerPattern == null) {
      integerPattern = patternCache.forName(buildIntegerPatternString());
    }
    return integerPattern;
  }

  /**
   * Fields and an accessor method to match line separators
   */
  private static volatile Pattern separatorPattern;
  private static volatile Pattern linePattern;
  private static final String LINE_SEPARATOR_PATTERN =
      "\r\n|[\n\r\u2028\u2029\u0085]";
  private static final String LINE_PATTERN = ".*(" + LINE_SEPARATOR_PATTERN + ")|.+$";

  private static Pattern separatorPattern() {
    Pattern sp = separatorPattern;
    if (sp == null) {
      separatorPattern = sp = Pattern.compile(LINE_SEPARATOR_PATTERN);
    }
    return sp;
  }

  private static Pattern linePattern() {
    Pattern lp = linePattern;
    if (lp == null) {
      linePattern = lp = Pattern.compile(LINE_PATTERN);
    }
    return lp;
  }

  /**
   * Fields and methods to match floats and doubles
   */
  private Pattern floatPattern;
  private Pattern decimalPattern;

  private void buildFloatAndDecimalPattern() {
    // \\p{javaDigit} may not be perfect, see above
    String digit = "([0-9]|(\\p{javaDigit}))";
    String exponent = "([eE][+-]?" + digit + "+)?";
    String groupedNumeral = "(" + non0Digit + digit + "?" + digit + "?(" +
        groupSeparator + digit + digit + digit + ")+)";
    // Once again digit++ is used for performance, as above
    String numeral = "((" + digit + "++)|" + groupedNumeral + ")";
    String decimalNumeral = "(" + numeral + "|" + numeral +
        decimalSeparator + digit + "*+|" + decimalSeparator +
        digit + "++)";
    String nonNumber = "(NaN|" + nanString + "|Infinity|" +
        infinityString + ")";
    String positiveFloat = "(" + positivePrefix + decimalNumeral +
        positiveSuffix + exponent + ")";
    String negativeFloat = "(" + negativePrefix + decimalNumeral +
        negativeSuffix + exponent + ")";
    String decimal = "(([-+]?" + decimalNumeral + exponent + ")|" +
        positiveFloat + "|" + negativeFloat + ")";
    String hexFloat =
        "[-+]?0[xX][0-9a-fA-F]*\\.[0-9a-fA-F]+([pP][-+]?[0-9]+)?";
    String positiveNonNumber = "(" + positivePrefix + nonNumber +
        positiveSuffix + ")";
    String negativeNonNumber = "(" + negativePrefix + nonNumber +
        negativeSuffix + ")";
    String signedNonNumber = "(([-+]?" + nonNumber + ")|" +
        positiveNonNumber + "|" +
        negativeNonNumber + ")";
    floatPattern = Pattern.compile(decimal + "|" + hexFloat + "|" +
        signedNonNumber);
    decimalPattern = Pattern.compile(decimal);
  }

  private Pattern floatPattern() {
    if (floatPattern == null) {
      buildFloatAndDecimalPattern();
    }
    return floatPattern;
  }

  private Pattern decimalPattern() {
    if (decimalPattern == null) {
      buildFloatAndDecimalPattern();
    }
    return decimalPattern;
  }

  // Constructors

  /**
   * Constructs a <code>Scanner</code> that returns values scanned
   * from the specified source delimited by the specified pattern.
   *
   * @param source A character source implementing the Readable interface
   * @param pattern A delimiting pattern
   */
  private Scanner(Readable source, Pattern pattern) {
    assert source != null : "source should not be null";
    assert pattern != null : "pattern should not be null";
    this.source = source;
    delimPattern = pattern;
    buf = CharBuffer.allocate(BUFFER_SIZE);
    buf.limit(0);
    matcher = delimPattern.matcher(buf);
    matcher.useTransparentBounds(true);
    matcher.useAnchoringBounds(false);
    useLocale(Locale.getDefault(Locale.Category.FORMAT));
  }

  /**
   * Constructs a new <code>Scanner</code> that produces values scanned
   * from the specified source.
   *
   * @param source A character source implementing the {@link Readable} interface
   */
  public Scanner(Readable source) {
    this(Objects.requireNonNull(source, "source"), WHITESPACE_PATTERN);
  }

  /**
   * Constructs a new <code>Scanner</code> that produces values scanned
   * from the specified input stream. Bytes from the stream are converted
   * into characters using the underlying platform's
   * {@linkplain java.nio.charset.Charset#defaultCharset() default charset}.
   *
   * @param source An input stream to be scanned
   */
  public Scanner(InputStream source) {
    this(new InputStreamReader(source), WHITESPACE_PATTERN);
  }

  /**
   * Constructs a new <code>Scanner</code> that produces values scanned
   * from the specified input stream. Bytes from the stream are converted
   * into characters using the specified charset.
   *
   * @param source An input stream to be scanned
   * @param charsetName The encoding type used to convert bytes from the stream into characters to
   * be scanned
   * @throws IllegalArgumentException if the specified character set does not exist
   */
  public Scanner(InputStream source, String charsetName) {
    this(makeReadable(Objects.requireNonNull(source, "source"), toCharset(charsetName)),
        WHITESPACE_PATTERN);
  }

  /**
   * Returns a charset object for the given charset name.
   *
   * @throws NullPointerException is csn is null
   * @throws IllegalArgumentException if the charset is not supported
   */
  private static Charset toCharset(String csn) {
    Objects.requireNonNull(csn, "charsetName");
    try {
      return Charset.forName(csn);
    } catch (IllegalCharsetNameException | UnsupportedCharsetException e) {
      // IllegalArgumentException should be thrown
      throw new IllegalArgumentException(e);
    }
  }

  private static Readable makeReadable(InputStream source, Charset charset) {
    return new InputStreamReader(source, charset);
  }

  /**
   * Constructs a new <code>Scanner</code> that produces values scanned
   * from the specified file. Bytes from the file are converted into
   * characters using the underlying platform's
   * {@linkplain java.nio.charset.Charset#defaultCharset() default charset}.
   *
   * @param source A file to be scanned
   * @throws FileNotFoundException if source is not found
   */
  public Scanner(File source) throws FileNotFoundException {
    this((ReadableByteChannel) (new FileInputStream(source).getChannel()));
  }

  /**
   * Constructs a new <code>Scanner</code> that produces values scanned
   * from the specified file. Bytes from the file are converted into
   * characters using the specified charset.
   *
   * @param source A file to be scanned
   * @param charsetName The encoding type used to convert bytes from the file into characters to be
   * scanned
   * @throws FileNotFoundException if source is not found
   * @throws IllegalArgumentException if the specified encoding is not found
   */
  public Scanner(File source, String charsetName)
      throws FileNotFoundException {
    this(Objects.requireNonNull(source), toDecoder(charsetName));
  }

  private Scanner(File source, CharsetDecoder dec)
      throws FileNotFoundException {
    this(makeReadable((ReadableByteChannel) (new FileInputStream(source).getChannel()), dec));
  }

  private static CharsetDecoder toDecoder(String charsetName) {
    Objects.requireNonNull(charsetName, "charsetName");
    try {
      return Charset.forName(charsetName).newDecoder();
    } catch (IllegalCharsetNameException | UnsupportedCharsetException unused) {
      throw new IllegalArgumentException(charsetName);
    }
  }

  private static Readable makeReadable(ReadableByteChannel source,
      CharsetDecoder dec) {
    return Channels.newReader(source, dec, -1);
  }

  /**
   * Constructs a new <code>Scanner</code> that produces values scanned
   * from the specified file. Bytes from the file are converted into
   * characters using the underlying platform's
   * {@linkplain java.nio.charset.Charset#defaultCharset() default charset}.
   *
   * @param source the path to the file to be scanned
   * @throws IOException if an I/O error occurs opening source
   * @since 1.7
   */
  public Scanner(Path source)
      throws IOException {
    this(Files.newInputStream(source));
  }

  /**
   * Constructs a new <code>Scanner</code> that produces values scanned
   * from the specified file. Bytes from the file are converted into
   * characters using the specified charset.
   *
   * @param source the path to the file to be scanned
   * @param charsetName The encoding type used to convert bytes from the file into characters to be
   * scanned
   * @throws IOException if an I/O error occurs opening source
   * @throws IllegalArgumentException if the specified encoding is not found
   * @since 1.7
   */
  public Scanner(Path source, String charsetName) throws IOException {
    this(Objects.requireNonNull(source), toCharset(charsetName));
  }

  private Scanner(Path source, Charset charset) throws IOException {
    this(makeReadable(Files.newInputStream(source), charset));
  }

  /**
   * Constructs a new <code>Scanner</code> that produces values scanned
   * from the specified string.
   *
   * @param source A string to scan
   */
  public Scanner(String source) {
    this(new StringReader(source), WHITESPACE_PATTERN);
  }

  /**
   * Constructs a new <code>Scanner</code> that produces values scanned
   * from the specified channel. Bytes from the source are converted into
   * characters using the underlying platform's
   * {@linkplain java.nio.charset.Charset#defaultCharset() default charset}.
   *
   * @param source A channel to scan
   */
  public Scanner(ReadableByteChannel source) {
    this(makeReadable(Objects.requireNonNull(source, "source")),
        WHITESPACE_PATTERN);
  }

  private static Readable makeReadable(ReadableByteChannel source) {
    return makeReadable(source, Charset.defaultCharset().newDecoder());
  }

  /**
   * Constructs a new <code>Scanner</code> that produces values scanned
   * from the specified channel. Bytes from the source are converted into
   * characters using the specified charset.
   *
   * @param source A channel to scan
   * @param charsetName The encoding type used to convert bytes from the channel into characters to
   * be scanned
   * @throws IllegalArgumentException if the specified character set does not exist
   */
  public Scanner(ReadableByteChannel source, String charsetName) {
    this(makeReadable(Objects.requireNonNull(source, "source"), toDecoder(charsetName)),
        WHITESPACE_PATTERN);
  }

  // Private primitives used to support scanning

  private void saveState() {
    savedScannerPosition = position;
  }

  private void revertState() {
    this.position = savedScannerPosition;
    savedScannerPosition = -1;
    skipped = false;
  }

  private boolean revertState(boolean b) {
    this.position = savedScannerPosition;
    savedScannerPosition = -1;
    skipped = false;
    return b;
  }

  private void cacheResult() {
    hasNextResult = matcher.group();
    hasNextPosition = matcher.end();
    hasNextPattern = matcher.pattern();
  }

  private void cacheResult(String result) {
    hasNextResult = result;
    hasNextPosition = matcher.end();
    hasNextPattern = matcher.pattern();
  }

  // Clears both regular cache and type cache
  private void clearCaches() {
    hasNextPattern = null;
    typeCache = null;
  }

  // Also clears both the regular cache and the type cache
  private String getCachedResult() {
    position = hasNextPosition;
    hasNextPattern = null;
    typeCache = null;
    return hasNextResult;
  }

  // Also clears both the regular cache and the type cache
  private void useTypeCache() {
    if (closed) {
      throw new IllegalStateException("Scanner closed");
    }
    position = hasNextPosition;
    hasNextPattern = null;
    typeCache = null;
  }

  // Tries to read more input. May block.
  private void readInput() {
    if (buf.limit() == buf.capacity()) {
      makeSpace();
    }

    // Prepare to receive data
    int p = buf.position();
    buf.position(buf.limit());
    buf.limit(buf.capacity());

    int n = 0;
    try {
      n = source.read(buf);
    } catch (IOException ioe) {
      lastException = ioe;
      n = -1;
    }

    if (n == -1) {
      sourceClosed = true;
      needInput = false;
    }

    if (n > 0) {
      needInput = false;
    }

    // Restore current position and limit for reading
    buf.limit(buf.position());
    buf.position(p);
  }

  // After this method is called there will either be an exception
  // or else there will be space in the buffer
  private boolean makeSpace() {
    clearCaches();
    int offset = savedScannerPosition == -1 ?
        position : savedScannerPosition;
    buf.position(offset);
    // Gain space by compacting buffer
    if (offset > 0) {
      buf.compact();
      translateSavedIndexes(offset);
      position -= offset;
      buf.flip();
      return true;
    }
    // Gain space by growing buffer
    int newSize = buf.capacity() * 2;
    CharBuffer newBuf = CharBuffer.allocate(newSize);
    newBuf.put(buf);
    newBuf.flip();
    translateSavedIndexes(offset);
    position -= offset;
    buf = newBuf;
    matcher.reset(buf);
    return true;
  }

  // When a buffer compaction/reallocation occurs the saved indexes must
  // be modified appropriately
  private void translateSavedIndexes(int offset) {
    if (savedScannerPosition != -1) {
      savedScannerPosition -= offset;
    }
  }

  // If we are at the end of input then NoSuchElement;
  // If there is still input left then InputMismatch
  private void throwFor() {
    skipped = false;
    if ((sourceClosed) && (position == buf.limit())) {
      throw new NoSuchElementException();
    } else {
      throw new InputMismatchException();
    }
  }

  // Returns true if a complete token or partial token is in the buffer.
  // It is not necessary to find a complete token since a partial token
  // means that there will be another token with or without more input.
  private boolean hasTokenInBuffer() {
    matchValid = false;
    matcher.usePattern(delimPattern);
    matcher.region(position, buf.limit());

    // Skip delims first
    if (matcher.lookingAt()) {
      position = matcher.end();
    }

    // If we are sitting at the end, no more tokens in buffer
    if (position == buf.limit()) {
      return false;
    }

    return true;
  }

  /*
   * Returns a "complete token" that matches the specified pattern
   *
   * A token is complete if surrounded by delims; a partial token
   * is prefixed by delims but not postfixed by them
   *
   * The position is advanced to the end of that complete token
   *
   * Pattern == null means accept any token at all
   *
   * Triple return:
   * 1. valid string means it was found
   * 2. null with needInput=false means we won't ever find it
   * 3. null with needInput=true means try again after readInput
   */
  private String getCompleteTokenInBuffer(Pattern pattern) {
    matchValid = false;

    // Skip delims first
    matcher.usePattern(delimPattern);
    if (!skipped) { // Enforcing only one skip of leading delims
      matcher.region(position, buf.limit());
      if (matcher.lookingAt()) {
        // If more input could extend the delimiters then we must wait
        // for more input
        if (matcher.hitEnd() && !sourceClosed) {
          needInput = true;
          return null;
        }
        // The delims were whole and the matcher should skip them
        skipped = true;
        position = matcher.end();
      }
    }

    // If we are sitting at the end, no more tokens in buffer
    if (position == buf.limit()) {
      if (sourceClosed) {
        return null;
      }
      needInput = true;
      return null;
    }

    // Must look for next delims. Simply attempting to match the
    // pattern at this point may find a match but it might not be
    // the first longest match because of missing input, or it might
    // match a partial token instead of the whole thing.

    // Then look for next delims
    matcher.region(position, buf.limit());
    boolean foundNextDelim = matcher.find();
    if (foundNextDelim && (matcher.end() == position)) {
      // Zero length delimiter match; we should find the next one
      // using the automatic advance past a zero length match;
      // Otherwise we have just found the same one we just skipped
      foundNextDelim = matcher.find();
    }
    if (foundNextDelim) {
      // In the rare case that more input could cause the match
      // to be lost and there is more input coming we must wait
      // for more input. Note that hitting the end is okay as long
      // as the match cannot go away. It is the beginning of the
      // next delims we want to be sure about, we don't care if
      // they potentially extend further.
      if (matcher.requireEnd() && !sourceClosed) {
        needInput = true;
        return null;
      }
      int tokenEnd = matcher.start();
      // There is a complete token.
      if (pattern == null) {
        // Must continue with match to provide valid MatchResult
        pattern = FIND_ANY_PATTERN;
      }
      //  Attempt to match against the desired pattern
      matcher.usePattern(pattern);
      matcher.region(position, tokenEnd);
      if (matcher.matches()) {
        String s = matcher.group();
        position = matcher.end();
        return s;
      } else { // Complete token but it does not match
        return null;
      }
    }

    // If we can't find the next delims but no more input is coming,
    // then we can treat the remainder as a whole token
    if (sourceClosed) {
      if (pattern == null) {
        // Must continue with match to provide valid MatchResult
        pattern = FIND_ANY_PATTERN;
      }
      // Last token; Match the pattern here or throw
      matcher.usePattern(pattern);
      matcher.region(position, buf.limit());
      if (matcher.matches()) {
        String s = matcher.group();
        position = matcher.end();
        return s;
      }
      // Last piece does not match
      return null;
    }

    // There is a partial token in the buffer; must read more
    // to complete it
    needInput = true;
    return null;
  }

  // Finds the specified pattern in the buffer up to horizon.
  // Returns a match for the specified input pattern.
  private String findPatternInBuffer(Pattern pattern, int horizon) {
    matchValid = false;
    matcher.usePattern(pattern);
    int bufferLimit = buf.limit();
    int horizonLimit = -1;
    int searchLimit = bufferLimit;
    if (horizon > 0) {
      horizonLimit = position + horizon;
      if (horizonLimit < bufferLimit) {
        searchLimit = horizonLimit;
      }
    }
    matcher.region(position, searchLimit);
    if (matcher.find()) {
      if (matcher.hitEnd() && (!sourceClosed)) {
        // The match may be longer if didn't hit horizon or real end
        if (searchLimit != horizonLimit) {
          // Hit an artificial end; try to extend the match
          needInput = true;
          return null;
        }
        // The match could go away depending on what is next
        if ((searchLimit == horizonLimit) && matcher.requireEnd()) {
          // Rare case: we hit the end of input and it happens
          // that it is at the horizon and the end of input is
          // required for the match.
          needInput = true;
          return null;
        }
      }
      // Did not hit end, or hit real end, or hit horizon
      position = matcher.end();
      return matcher.group();
    }

    if (sourceClosed) {
      return null;
    }

    // If there is no specified horizon, or if we have not searched
    // to the specified horizon yet, get more input
    if ((horizon == 0) || (searchLimit != horizonLimit)) {
      needInput = true;
    }
    return null;
  }

  // Returns a match for the specified input pattern anchored at
  // the current position
  private String matchPatternInBuffer(Pattern pattern) {
    matchValid = false;
    matcher.usePattern(pattern);
    matcher.region(position, buf.limit());
    if (matcher.lookingAt()) {
      if (matcher.hitEnd() && (!sourceClosed)) {
        // Get more input and try again
        needInput = true;
        return null;
      }
      position = matcher.end();
      return matcher.group();
    }

    if (sourceClosed) {
      return null;
    }

    // Read more to find pattern
    needInput = true;
    return null;
  }

  // Throws if the scanner is closed
  private void ensureOpen() {
    if (closed) {
      throw new IllegalStateException("Scanner closed");
    }
  }

  // Public methods

  /**
   * Closes this scanner.
   *
   * <p> If this scanner has not yet been closed then if its underlying
   * {@linkplain java.lang.Readable readable} also implements the {@link
   * java.io.Closeable} interface then the readable's <tt>close</tt> method
   * will be invoked.  If this scanner is already closed then invoking this
   * method will have no effect.
   *
   * <p>Attempting to perform search operations after a scanner has
   * been closed will result in an {@link IllegalStateException}.
   */
  public void close() {
    if (closed) {
      return;
    }
    if (source instanceof Closeable) {
      try {
        ((Closeable) source).close();
      } catch (IOException ioe) {
        lastException = ioe;
      }
    }
    sourceClosed = true;
    source = null;
    closed = true;
  }

  /**
   * Returns the <code>IOException</code> last thrown by this
   * <code>Scanner</code>'s underlying <code>Readable</code>. This method
   * returns <code>null</code> if no such exception exists.
   *
   * @return the last exception thrown by this scanner's readable
   */
  public IOException ioException() {
    return lastException;
  }

  /**
   * Returns the <code>Pattern</code> this <code>Scanner</code> is currently
   * using to match delimiters.
   *
   * @return this scanner's delimiting pattern.
   */
  public Pattern delimiter() {
    return delimPattern;
  }

  /**
   * Sets this scanner's delimiting pattern to the specified pattern.
   *
   * @param pattern A delimiting pattern
   * @return this scanner
   */
  public Scanner useDelimiter(Pattern pattern) {
    delimPattern = pattern;
    return this;
  }

  /**
   * Sets this scanner's delimiting pattern to a pattern constructed from
   * the specified <code>String</code>.
   *
   * <p> An invocation of this method of the form
   * <tt>useDelimiter(pattern)</tt> behaves in exactly the same way as the
   * invocation <tt>useDelimiter(Pattern.compile(pattern))</tt>.
   *
   * <p> Invoking the {@link #reset} method will set the scanner's delimiter
   * to the <a href= "#default-delimiter">default</a>.
   *
   * @param pattern A string specifying a delimiting pattern
   * @return this scanner
   */
  public Scanner useDelimiter(String pattern) {
    delimPattern = patternCache.forName(pattern);
    return this;
  }

  /**
   * Returns this scanner's locale.
   *
   * <p>A scanner's locale affects many elements of its default
   * primitive matching regular expressions; see
   * <a href= "#localized-numbers">localized numbers</a> above.
   *
   * @return this scanner's locale
   */
  public Locale locale() {
    return this.locale;
  }

  /**
   * Sets this scanner's locale to the specified locale.
   *
   * <p>A scanner's locale affects many elements of its default
   * primitive matching regular expressions; see
   * <a href= "#localized-numbers">localized numbers</a> above.
   *
   * <p>Invoking the {@link #reset} method will set the scanner's locale to
   * the <a href= "#initial-locale">initial locale</a>.
   *
   * @param locale A string specifying the locale to use
   * @return this scanner
   */
  public Scanner useLocale(Locale locale) {
    if (locale.equals(this.locale)) {
      return this;
    }

    this.locale = locale;
    DecimalFormat df =
        (DecimalFormat) NumberFormat.getNumberInstance(locale);
    DecimalFormatSymbols dfs = DecimalFormatSymbols.getInstance(locale);

    // These must be literalized to avoid collision with regex
    // metacharacters such as dot or parenthesis
    groupSeparator = "\\" + dfs.getGroupingSeparator();
    decimalSeparator = "\\" + dfs.getDecimalSeparator();

    // Quoting the nonzero length locale-specific things
    // to avoid potential conflict with metacharacters
    nanString = "\\Q" + dfs.getNaN() + "\\E";
    infinityString = "\\Q" + dfs.getInfinity() + "\\E";
    positivePrefix = df.getPositivePrefix();
    if (positivePrefix.length() > 0) {
      positivePrefix = "\\Q" + positivePrefix + "\\E";
    }
    negativePrefix = df.getNegativePrefix();
    if (negativePrefix.length() > 0) {
      negativePrefix = "\\Q" + negativePrefix + "\\E";
    }
    positiveSuffix = df.getPositiveSuffix();
    if (positiveSuffix.length() > 0) {
      positiveSuffix = "\\Q" + positiveSuffix + "\\E";
    }
    negativeSuffix = df.getNegativeSuffix();
    if (negativeSuffix.length() > 0) {
      negativeSuffix = "\\Q" + negativeSuffix + "\\E";
    }

    // Force rebuilding and recompilation of locale dependent
    // primitive patterns
    integerPattern = null;
    floatPattern = null;

    return this;
  }

  /**
   * Returns this scanner's default radix.
   *
   * <p>A scanner's radix affects elements of its default
   * number matching regular expressions; see
   * <a href= "#localized-numbers">localized numbers</a> above.
   *
   * @return the default radix of this scanner
   */
  public int radix() {
    return this.defaultRadix;
  }

  /**
   * Sets this scanner's default radix to the specified radix.
   *
   * <p>A scanner's radix affects elements of its default
   * number matching regular expressions; see
   * <a href= "#localized-numbers">localized numbers</a> above.
   *
   * <p>If the radix is less than <code>Character.MIN_RADIX</code>
   * or greater than <code>Character.MAX_RADIX</code>, then an
   * <code>IllegalArgumentException</code> is thrown.
   *
   * <p>Invoking the {@link #reset} method will set the scanner's radix to
   * <code>10</code>.
   *
   * @param radix The radix to use when scanning numbers
   * @return this scanner
   * @throws IllegalArgumentException if radix is out of range
   */
  public Scanner useRadix(int radix) {
    if ((radix < Character.MIN_RADIX) || (radix > Character.MAX_RADIX)) {
      throw new IllegalArgumentException("radix:" + radix);
    }

    if (this.defaultRadix == radix) {
      return this;
    }
    this.defaultRadix = radix;
    // Force rebuilding and recompilation of radix dependent patterns
    integerPattern = null;
    return this;
  }

  // The next operation should occur in the specified radix but
  // the default is left untouched.
  private void setRadix(int radix) {
    if (this.radix != radix) {
      // Force rebuilding and recompilation of radix dependent patterns
      integerPattern = null;
      this.radix = radix;
    }
  }

  /**
   * Returns the match result of the last scanning operation performed
   * by this scanner. This method throws <code>IllegalStateException</code>
   * if no match has been performed, or if the last match was
   * not successful.
   *
   * <p>The various <code>next</code>methods of <code>Scanner</code>
   * make a match result available if they complete without throwing an
   * exception. For instance, after an invocation of the {@link #nextInt}
   * method that returned an int, this method returns a
   * <code>MatchResult</code> for the search of the
   * <a href="#Integer-regex"><i>Integer</i></a> regular expression
   * defined above. Similarly the {@link #findInLine},
   * {@link #findWithinHorizon}, and {@link #skip} methods will make a
   * match available if they succeed.
   *
   * @return a match result for the last match operation
   * @throws IllegalStateException If no match result is available
   */
  public MatchResult match() {
    if (!matchValid) {
      throw new IllegalStateException("No match result available");
    }
    return matcher.toMatchResult();
  }

  /**
   * <p>Returns the string representation of this <code>Scanner</code>. The
   * string representation of a <code>Scanner</code> contains information
   * that may be useful for debugging. The exact format is unspecified.
   *
   * @return The string representation of this scanner
   */
  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append("java.util.Scanner");
    sb.append("[delimiters=" + delimPattern + "]");
    sb.append("[position=" + position + "]");
    sb.append("[match valid=" + matchValid + "]");
    sb.append("[need input=" + needInput + "]");
    sb.append("[source closed=" + sourceClosed + "]");
    sb.append("[skipped=" + skipped + "]");
    sb.append("[group separator=" + groupSeparator + "]");
    sb.append("[decimal separator=" + decimalSeparator + "]");
    sb.append("[positive prefix=" + positivePrefix + "]");
    sb.append("[negative prefix=" + negativePrefix + "]");
    sb.append("[positive suffix=" + positiveSuffix + "]");
    sb.append("[negative suffix=" + negativeSuffix + "]");
    sb.append("[NaN string=" + nanString + "]");
    sb.append("[infinity string=" + infinityString + "]");
    return sb.toString();
  }

  /**
   * Returns true if this scanner has another token in its input.
   * This method may block while waiting for input to scan.
   * The scanner does not advance past any input.
   *
   * @return true if and only if this scanner has another token
   * @throws IllegalStateException if this scanner is closed
   * @see java.util.Iterator
   */
  public boolean hasNext() {
    ensureOpen();
    saveState();
    while (!sourceClosed) {
      if (hasTokenInBuffer()) {
        return revertState(true);
      }
      readInput();
    }
    boolean result = hasTokenInBuffer();
    return revertState(result);
  }

  /**
   * Finds and returns the next complete token from this scanner.
   * A complete token is preceded and followed by input that matches
   * the delimiter pattern. This method may block while waiting for input
   * to scan, even if a previous invocation of {@link #hasNext} returned
   * <code>true</code>.
   *
   * @return the next token
   * @throws NoSuchElementException if no more tokens are available
   * @throws IllegalStateException if this scanner is closed
   * @see java.util.Iterator
   */
  public String next() {
    ensureOpen();
    clearCaches();

    while (true) {
      String token = getCompleteTokenInBuffer(null);
      if (token != null) {
        matchValid = true;
        skipped = false;
        return token;
      }
      if (needInput) {
        readInput();
      } else {
        throwFor();
      }
    }
  }

  /**
   * The remove operation is not supported by this implementation of
   * <code>Iterator</code>.
   *
   * @throws UnsupportedOperationException if this method is invoked.
   * @see java.util.Iterator
   */
  public void remove() {
    throw new UnsupportedOperationException();
  }

  /**
   * Returns true if the next token matches the pattern constructed from the
   * specified string. The scanner does not advance past any input.
   *
   * <p> An invocation of this method of the form <tt>hasNext(pattern)</tt>
   * behaves in exactly the same way as the invocation
   * <tt>hasNext(Pattern.compile(pattern))</tt>.
   *
   * @param pattern a string specifying the pattern to scan
   * @return true if and only if this scanner has another token matching the specified pattern
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNext(String pattern) {
    return hasNext(patternCache.forName(pattern));
  }

  /**
   * Returns the next token if it matches the pattern constructed from the
   * specified string.  If the match is successful, the scanner advances
   * past the input that matched the pattern.
   *
   * <p> An invocation of this method of the form <tt>next(pattern)</tt>
   * behaves in exactly the same way as the invocation
   * <tt>next(Pattern.compile(pattern))</tt>.
   *
   * @param pattern a string specifying the pattern to scan
   * @return the next token
   * @throws NoSuchElementException if no such tokens are available
   * @throws IllegalStateException if this scanner is closed
   */
  public String next(String pattern) {
    return next(patternCache.forName(pattern));
  }

  /**
   * Returns true if the next complete token matches the specified pattern.
   * A complete token is prefixed and postfixed by input that matches
   * the delimiter pattern. This method may block while waiting for input.
   * The scanner does not advance past any input.
   *
   * @param pattern the pattern to scan for
   * @return true if and only if this scanner has another token matching the specified pattern
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNext(Pattern pattern) {
    ensureOpen();
    if (pattern == null) {
      throw new NullPointerException();
    }
    hasNextPattern = null;
    saveState();

    while (true) {
      if (getCompleteTokenInBuffer(pattern) != null) {
        matchValid = true;
        cacheResult();
        return revertState(true);
      }
      if (needInput) {
        readInput();
      } else {
        return revertState(false);
      }
    }
  }

  /**
   * Returns the next token if it matches the specified pattern. This
   * method may block while waiting for input to scan, even if a previous
   * invocation of {@link #hasNext(Pattern)} returned <code>true</code>.
   * If the match is successful, the scanner advances past the input that
   * matched the pattern.
   *
   * @param pattern the pattern to scan for
   * @return the next token
   * @throws NoSuchElementException if no more tokens are available
   * @throws IllegalStateException if this scanner is closed
   */
  public String next(Pattern pattern) {
    ensureOpen();
    if (pattern == null) {
      throw new NullPointerException();
    }

    // Did we already find this pattern?
    if (hasNextPattern == pattern) {
      return getCachedResult();
    }
    clearCaches();

    // Search for the pattern
    while (true) {
      String token = getCompleteTokenInBuffer(pattern);
      if (token != null) {
        matchValid = true;
        skipped = false;
        return token;
      }
      if (needInput) {
        readInput();
      } else {
        throwFor();
      }
    }
  }

  /**
   * Returns true if there is another line in the input of this scanner.
   * This method may block while waiting for input. The scanner does not
   * advance past any input.
   *
   * @return true if and only if this scanner has another line of input
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNextLine() {
    saveState();

    String result = findWithinHorizon(linePattern(), 0);
    if (result != null) {
      MatchResult mr = this.match();
      String lineSep = mr.group(1);
      if (lineSep != null) {
        result = result.substring(0, result.length() -
            lineSep.length());
        cacheResult(result);

      } else {
        cacheResult();
      }
    }
    revertState();
    return (result != null);
  }

  /**
   * Advances this scanner past the current line and returns the input
   * that was skipped.
   *
   * This method returns the rest of the current line, excluding any line
   * separator at the end. The position is set to the beginning of the next
   * line.
   *
   * <p>Since this method continues to search through the input looking
   * for a line separator, it may buffer all of the input searching for
   * the line to skip if no line separators are present.
   *
   * @return the line that was skipped
   * @throws NoSuchElementException if no line was found
   * @throws IllegalStateException if this scanner is closed
   */
  public String nextLine() {
    if (hasNextPattern == linePattern()) {
      return getCachedResult();
    }
    clearCaches();

    String result = findWithinHorizon(linePattern, 0);
    if (result == null) {
      throw new NoSuchElementException("No line found");
    }
    MatchResult mr = this.match();
    String lineSep = mr.group(1);
    if (lineSep != null) {
      result = result.substring(0, result.length() - lineSep.length());
    }
    if (result == null) {
      throw new NoSuchElementException();
    } else {
      return result;
    }
  }

  // Public methods that ignore delimiters

  /**
   * Attempts to find the next occurrence of a pattern constructed from the
   * specified string, ignoring delimiters.
   *
   * <p>An invocation of this method of the form <tt>findInLine(pattern)</tt>
   * behaves in exactly the same way as the invocation
   * <tt>findInLine(Pattern.compile(pattern))</tt>.
   *
   * @param pattern a string specifying the pattern to search for
   * @return the text that matched the specified pattern
   * @throws IllegalStateException if this scanner is closed
   */
  public String findInLine(String pattern) {
    return findInLine(patternCache.forName(pattern));
  }

  /**
   * Attempts to find the next occurrence of the specified pattern ignoring
   * delimiters. If the pattern is found before the next line separator, the
   * scanner advances past the input that matched and returns the string that
   * matched the pattern.
   * If no such pattern is detected in the input up to the next line
   * separator, then <code>null</code> is returned and the scanner's
   * position is unchanged. This method may block waiting for input that
   * matches the pattern.
   *
   * <p>Since this method continues to search through the input looking
   * for the specified pattern, it may buffer all of the input searching for
   * the desired token if no line separators are present.
   *
   * @param pattern the pattern to scan for
   * @return the text that matched the specified pattern
   * @throws IllegalStateException if this scanner is closed
   */
  public String findInLine(Pattern pattern) {
    ensureOpen();
    if (pattern == null) {
      throw new NullPointerException();
    }
    clearCaches();
    // Expand buffer to include the next newline or end of input
    int endPosition = 0;
    saveState();
    while (true) {
      String token = findPatternInBuffer(separatorPattern(), 0);
      if (token != null) {
        endPosition = matcher.start();
        break; // up to next newline
      }
      if (needInput) {
        readInput();
      } else {
        endPosition = buf.limit();
        break; // up to end of input
      }
    }
    revertState();
    int horizonForLine = endPosition - position;
    // If there is nothing between the current pos and the next
    // newline simply return null, invoking findWithinHorizon
    // with "horizon=0" will scan beyond the line bound.
    if (horizonForLine == 0) {
      return null;
    }
    // Search for the pattern
    return findWithinHorizon(pattern, horizonForLine);
  }

  /**
   * Attempts to find the next occurrence of a pattern constructed from the
   * specified string, ignoring delimiters.
   *
   * <p>An invocation of this method of the form
   * <tt>findWithinHorizon(pattern)</tt> behaves in exactly the same way as
   * the invocation
   * <tt>findWithinHorizon(Pattern.compile(pattern, horizon))</tt>.
   *
   * @param pattern a string specifying the pattern to search for
   * @param horizon the search horizon
   * @return the text that matched the specified pattern
   * @throws IllegalStateException if this scanner is closed
   * @throws IllegalArgumentException if horizon is negative
   */
  public String findWithinHorizon(String pattern, int horizon) {
    return findWithinHorizon(patternCache.forName(pattern), horizon);
  }

  /**
   * Attempts to find the next occurrence of the specified pattern.
   *
   * <p>This method searches through the input up to the specified
   * search horizon, ignoring delimiters. If the pattern is found the
   * scanner advances past the input that matched and returns the string
   * that matched the pattern. If no such pattern is detected then the
   * null is returned and the scanner's position remains unchanged. This
   * method may block waiting for input that matches the pattern.
   *
   * <p>A scanner will never search more than <code>horizon</code> code
   * points beyond its current position. Note that a match may be clipped
   * by the horizon; that is, an arbitrary match result may have been
   * different if the horizon had been larger. The scanner treats the
   * horizon as a transparent, non-anchoring bound (see {@link
   * Matcher#useTransparentBounds} and {@link Matcher#useAnchoringBounds}).
   *
   * <p>If horizon is <code>0</code>, then the horizon is ignored and
   * this method continues to search through the input looking for the
   * specified pattern without bound. In this case it may buffer all of
   * the input searching for the pattern.
   *
   * <p>If horizon is negative, then an IllegalArgumentException is
   * thrown.
   *
   * @param pattern the pattern to scan for
   * @param horizon the search horizon
   * @return the text that matched the specified pattern
   * @throws IllegalStateException if this scanner is closed
   * @throws IllegalArgumentException if horizon is negative
   */
  public String findWithinHorizon(Pattern pattern, int horizon) {
    ensureOpen();
    if (pattern == null) {
      throw new NullPointerException();
    }
    if (horizon < 0) {
      throw new IllegalArgumentException("horizon < 0");
    }
    clearCaches();

    // Search for the pattern
    while (true) {
      String token = findPatternInBuffer(pattern, horizon);
      if (token != null) {
        matchValid = true;
        return token;
      }
      if (needInput) {
        readInput();
      } else {
        break; // up to end of input
      }
    }
    return null;
  }

  /**
   * Skips input that matches the specified pattern, ignoring delimiters.
   * This method will skip input if an anchored match of the specified
   * pattern succeeds.
   *
   * <p>If a match to the specified pattern is not found at the
   * current position, then no input is skipped and a
   * <tt>NoSuchElementException</tt> is thrown.
   *
   * <p>Since this method seeks to match the specified pattern starting at
   * the scanner's current position, patterns that can match a lot of
   * input (".*", for example) may cause the scanner to buffer a large
   * amount of input.
   *
   * <p>Note that it is possible to skip something without risking a
   * <code>NoSuchElementException</code> by using a pattern that can
   * match nothing, e.g., <code>sc.skip("[ \t]*")</code>.
   *
   * @param pattern a string specifying the pattern to skip over
   * @return this scanner
   * @throws NoSuchElementException if the specified pattern is not found
   * @throws IllegalStateException if this scanner is closed
   */
  public Scanner skip(Pattern pattern) {
    ensureOpen();
    if (pattern == null) {
      throw new NullPointerException();
    }
    clearCaches();

    // Search for the pattern
    while (true) {
      String token = matchPatternInBuffer(pattern);
      if (token != null) {
        matchValid = true;
        position = matcher.end();
        return this;
      }
      if (needInput) {
        readInput();
      } else {
        throw new NoSuchElementException();
      }
    }
  }

  /**
   * Skips input that matches a pattern constructed from the specified
   * string.
   *
   * <p> An invocation of this method of the form <tt>skip(pattern)</tt>
   * behaves in exactly the same way as the invocation
   * <tt>skip(Pattern.compile(pattern))</tt>.
   *
   * @param pattern a string specifying the pattern to skip over
   * @return this scanner
   * @throws IllegalStateException if this scanner is closed
   */
  public Scanner skip(String pattern) {
    return skip(patternCache.forName(pattern));
  }

  // Convenience methods for scanning primitives

  /**
   * Returns true if the next token in this scanner's input can be
   * interpreted as a boolean value using a case insensitive pattern
   * created from the string "true|false".  The scanner does not
   * advance past the input that matched.
   *
   * @return true if and only if this scanner's next token is a valid boolean value
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNextBoolean() {
    return hasNext(boolPattern());
  }

  /**
   * Scans the next token of the input into a boolean value and returns
   * that value. This method will throw <code>InputMismatchException</code>
   * if the next token cannot be translated into a valid boolean value.
   * If the match is successful, the scanner advances past the input that
   * matched.
   *
   * @return the boolean scanned from the input
   * @throws InputMismatchException if the next token is not a valid boolean
   * @throws NoSuchElementException if input is exhausted
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean nextBoolean() {
    clearCaches();
    return Boolean.parseBoolean(next(boolPattern()));
  }

  /**
   * Returns true if the next token in this scanner's input can be
   * interpreted as a byte value in the default radix using the
   * {@link #nextByte} method. The scanner does not advance past any input.
   *
   * @return true if and only if this scanner's next token is a valid byte value
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNextByte() {
    return hasNextByte(defaultRadix);
  }

  /**
   * Returns true if the next token in this scanner's input can be
   * interpreted as a byte value in the specified radix using the
   * {@link #nextByte} method. The scanner does not advance past any input.
   *
   * @param radix the radix used to interpret the token as a byte value
   * @return true if and only if this scanner's next token is a valid byte value
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNextByte(int radix) {
    setRadix(radix);
    boolean result = hasNext(integerPattern());
    if (result) { // Cache it
      try {
        String s = (matcher.group(SIMPLE_GROUP_INDEX) == null) ?
            processIntegerToken(hasNextResult) :
            hasNextResult;
        typeCache = Byte.parseByte(s, radix);
      } catch (NumberFormatException nfe) {
        result = false;
      }
    }
    return result;
  }

  /**
   * Scans the next token of the input as a <tt>byte</tt>.
   *
   * <p> An invocation of this method of the form
   * <tt>nextByte()</tt> behaves in exactly the same way as the
   * invocation <tt>nextByte(radix)</tt>, where <code>radix</code>
   * is the default radix of this scanner.
   *
   * @return the <tt>byte</tt> scanned from the input
   * @throws InputMismatchException if the next token does not match the <i>Integer</i> regular
   * expression, or is out of range
   * @throws NoSuchElementException if input is exhausted
   * @throws IllegalStateException if this scanner is closed
   */
  public byte nextByte() {
    return nextByte(defaultRadix);
  }

  /**
   * Scans the next token of the input as a <tt>byte</tt>.
   * This method will throw <code>InputMismatchException</code>
   * if the next token cannot be translated into a valid byte value as
   * described below. If the translation is successful, the scanner advances
   * past the input that matched.
   *
   * <p> If the next token matches the <a
   * href="#Integer-regex"><i>Integer</i></a> regular expression defined
   * above then the token is converted into a <tt>byte</tt> value as if by
   * removing all locale specific prefixes, group separators, and locale
   * specific suffixes, then mapping non-ASCII digits into ASCII
   * digits via {@link Character#digit Character.digit}, prepending a
   * negative sign (-) if the locale specific negative prefixes and suffixes
   * were present, and passing the resulting string to
   * {@link Byte#parseByte(String, int) Byte.parseByte} with the
   * specified radix.
   *
   * @param radix the radix used to interpret the token as a byte value
   * @return the <tt>byte</tt> scanned from the input
   * @throws InputMismatchException if the next token does not match the <i>Integer</i> regular
   * expression, or is out of range
   * @throws NoSuchElementException if input is exhausted
   * @throws IllegalStateException if this scanner is closed
   */
  public byte nextByte(int radix) {
    // Check cached result
    if ((typeCache != null) && (typeCache instanceof Byte)
        && this.radix == radix) {
      byte val = ((Byte) typeCache).byteValue();
      useTypeCache();
      return val;
    }
    setRadix(radix);
    clearCaches();
    // Search for next byte
    try {
      String s = next(integerPattern());
      if (matcher.group(SIMPLE_GROUP_INDEX) == null) {
        s = processIntegerToken(s);
      }
      return Byte.parseByte(s, radix);
    } catch (NumberFormatException nfe) {
      position = matcher.start(); // don't skip bad token
      throw new InputMismatchException(nfe.getMessage());
    }
  }

  /**
   * Returns true if the next token in this scanner's input can be
   * interpreted as a short value in the default radix using the
   * {@link #nextShort} method. The scanner does not advance past any input.
   *
   * @return true if and only if this scanner's next token is a valid short value in the default
   * radix
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNextShort() {
    return hasNextShort(defaultRadix);
  }

  /**
   * Returns true if the next token in this scanner's input can be
   * interpreted as a short value in the specified radix using the
   * {@link #nextShort} method. The scanner does not advance past any input.
   *
   * @param radix the radix used to interpret the token as a short value
   * @return true if and only if this scanner's next token is a valid short value in the specified
   * radix
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNextShort(int radix) {
    setRadix(radix);
    boolean result = hasNext(integerPattern());
    if (result) { // Cache it
      try {
        String s = (matcher.group(SIMPLE_GROUP_INDEX) == null) ?
            processIntegerToken(hasNextResult) :
            hasNextResult;
        typeCache = Short.parseShort(s, radix);
      } catch (NumberFormatException nfe) {
        result = false;
      }
    }
    return result;
  }

  /**
   * Scans the next token of the input as a <tt>short</tt>.
   *
   * <p> An invocation of this method of the form
   * <tt>nextShort()</tt> behaves in exactly the same way as the
   * invocation <tt>nextShort(radix)</tt>, where <code>radix</code>
   * is the default radix of this scanner.
   *
   * @return the <tt>short</tt> scanned from the input
   * @throws InputMismatchException if the next token does not match the <i>Integer</i> regular
   * expression, or is out of range
   * @throws NoSuchElementException if input is exhausted
   * @throws IllegalStateException if this scanner is closed
   */
  public short nextShort() {
    return nextShort(defaultRadix);
  }

  /**
   * Scans the next token of the input as a <tt>short</tt>.
   * This method will throw <code>InputMismatchException</code>
   * if the next token cannot be translated into a valid short value as
   * described below. If the translation is successful, the scanner advances
   * past the input that matched.
   *
   * <p> If the next token matches the <a
   * href="#Integer-regex"><i>Integer</i></a> regular expression defined
   * above then the token is converted into a <tt>short</tt> value as if by
   * removing all locale specific prefixes, group separators, and locale
   * specific suffixes, then mapping non-ASCII digits into ASCII
   * digits via {@link Character#digit Character.digit}, prepending a
   * negative sign (-) if the locale specific negative prefixes and suffixes
   * were present, and passing the resulting string to
   * {@link Short#parseShort(String, int) Short.parseShort} with the
   * specified radix.
   *
   * @param radix the radix used to interpret the token as a short value
   * @return the <tt>short</tt> scanned from the input
   * @throws InputMismatchException if the next token does not match the <i>Integer</i> regular
   * expression, or is out of range
   * @throws NoSuchElementException if input is exhausted
   * @throws IllegalStateException if this scanner is closed
   */
  public short nextShort(int radix) {
    // Check cached result
    if ((typeCache != null) && (typeCache instanceof Short)
        && this.radix == radix) {
      short val = ((Short) typeCache).shortValue();
      useTypeCache();
      return val;
    }
    setRadix(radix);
    clearCaches();
    // Search for next short
    try {
      String s = next(integerPattern());
      if (matcher.group(SIMPLE_GROUP_INDEX) == null) {
        s = processIntegerToken(s);
      }
      return Short.parseShort(s, radix);
    } catch (NumberFormatException nfe) {
      position = matcher.start(); // don't skip bad token
      throw new InputMismatchException(nfe.getMessage());
    }
  }

  /**
   * Returns true if the next token in this scanner's input can be
   * interpreted as an int value in the default radix using the
   * {@link #nextInt} method. The scanner does not advance past any input.
   *
   * @return true if and only if this scanner's next token is a valid int value
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNextInt() {
    return hasNextInt(defaultRadix);
  }

  /**
   * Returns true if the next token in this scanner's input can be
   * interpreted as an int value in the specified radix using the
   * {@link #nextInt} method. The scanner does not advance past any input.
   *
   * @param radix the radix used to interpret the token as an int value
   * @return true if and only if this scanner's next token is a valid int value
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNextInt(int radix) {
    setRadix(radix);
    boolean result = hasNext(integerPattern());
    if (result) { // Cache it
      try {
        String s = (matcher.group(SIMPLE_GROUP_INDEX) == null) ?
            processIntegerToken(hasNextResult) :
            hasNextResult;
        typeCache = Integer.parseInt(s, radix);
      } catch (NumberFormatException nfe) {
        result = false;
      }
    }
    return result;
  }

  /**
   * The integer token must be stripped of prefixes, group separators,
   * and suffixes, non ascii digits must be converted into ascii digits
   * before parse will accept it.
   */
  private String processIntegerToken(String token) {
    String result = token.replaceAll("" + groupSeparator, "");
    boolean isNegative = false;
    int preLen = negativePrefix.length();
    if ((preLen > 0) && result.startsWith(negativePrefix)) {
      isNegative = true;
      result = result.substring(preLen);
    }
    int sufLen = negativeSuffix.length();
    if ((sufLen > 0) && result.endsWith(negativeSuffix)) {
      isNegative = true;
      result = result.substring(result.length() - sufLen,
          result.length());
    }
    if (isNegative) {
      result = "-" + result;
    }
    return result;
  }

  /**
   * Scans the next token of the input as an <tt>int</tt>.
   *
   * <p> An invocation of this method of the form
   * <tt>nextInt()</tt> behaves in exactly the same way as the
   * invocation <tt>nextInt(radix)</tt>, where <code>radix</code>
   * is the default radix of this scanner.
   *
   * @return the <tt>int</tt> scanned from the input
   * @throws InputMismatchException if the next token does not match the <i>Integer</i> regular
   * expression, or is out of range
   * @throws NoSuchElementException if input is exhausted
   * @throws IllegalStateException if this scanner is closed
   */
  public int nextInt() {
    return nextInt(defaultRadix);
  }

  /**
   * Scans the next token of the input as an <tt>int</tt>.
   * This method will throw <code>InputMismatchException</code>
   * if the next token cannot be translated into a valid int value as
   * described below. If the translation is successful, the scanner advances
   * past the input that matched.
   *
   * <p> If the next token matches the <a
   * href="#Integer-regex"><i>Integer</i></a> regular expression defined
   * above then the token is converted into an <tt>int</tt> value as if by
   * removing all locale specific prefixes, group separators, and locale
   * specific suffixes, then mapping non-ASCII digits into ASCII
   * digits via {@link Character#digit Character.digit}, prepending a
   * negative sign (-) if the locale specific negative prefixes and suffixes
   * were present, and passing the resulting string to
   * {@link Integer#parseInt(String, int) Integer.parseInt} with the
   * specified radix.
   *
   * @param radix the radix used to interpret the token as an int value
   * @return the <tt>int</tt> scanned from the input
   * @throws InputMismatchException if the next token does not match the <i>Integer</i> regular
   * expression, or is out of range
   * @throws NoSuchElementException if input is exhausted
   * @throws IllegalStateException if this scanner is closed
   */
  public int nextInt(int radix) {
    // Check cached result
    if ((typeCache != null) && (typeCache instanceof Integer)
        && this.radix == radix) {
      int val = ((Integer) typeCache).intValue();
      useTypeCache();
      return val;
    }
    setRadix(radix);
    clearCaches();
    // Search for next int
    try {
      String s = next(integerPattern());
      if (matcher.group(SIMPLE_GROUP_INDEX) == null) {
        s = processIntegerToken(s);
      }
      return Integer.parseInt(s, radix);
    } catch (NumberFormatException nfe) {
      position = matcher.start(); // don't skip bad token
      throw new InputMismatchException(nfe.getMessage());
    }
  }

  /**
   * Returns true if the next token in this scanner's input can be
   * interpreted as a long value in the default radix using the
   * {@link #nextLong} method. The scanner does not advance past any input.
   *
   * @return true if and only if this scanner's next token is a valid long value
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNextLong() {
    return hasNextLong(defaultRadix);
  }

  /**
   * Returns true if the next token in this scanner's input can be
   * interpreted as a long value in the specified radix using the
   * {@link #nextLong} method. The scanner does not advance past any input.
   *
   * @param radix the radix used to interpret the token as a long value
   * @return true if and only if this scanner's next token is a valid long value
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNextLong(int radix) {
    setRadix(radix);
    boolean result = hasNext(integerPattern());
    if (result) { // Cache it
      try {
        String s = (matcher.group(SIMPLE_GROUP_INDEX) == null) ?
            processIntegerToken(hasNextResult) :
            hasNextResult;
        typeCache = Long.parseLong(s, radix);
      } catch (NumberFormatException nfe) {
        result = false;
      }
    }
    return result;
  }

  /**
   * Scans the next token of the input as a <tt>long</tt>.
   *
   * <p> An invocation of this method of the form
   * <tt>nextLong()</tt> behaves in exactly the same way as the
   * invocation <tt>nextLong(radix)</tt>, where <code>radix</code>
   * is the default radix of this scanner.
   *
   * @return the <tt>long</tt> scanned from the input
   * @throws InputMismatchException if the next token does not match the <i>Integer</i> regular
   * expression, or is out of range
   * @throws NoSuchElementException if input is exhausted
   * @throws IllegalStateException if this scanner is closed
   */
  public long nextLong() {
    return nextLong(defaultRadix);
  }

  /**
   * Scans the next token of the input as a <tt>long</tt>.
   * This method will throw <code>InputMismatchException</code>
   * if the next token cannot be translated into a valid long value as
   * described below. If the translation is successful, the scanner advances
   * past the input that matched.
   *
   * <p> If the next token matches the <a
   * href="#Integer-regex"><i>Integer</i></a> regular expression defined
   * above then the token is converted into a <tt>long</tt> value as if by
   * removing all locale specific prefixes, group separators, and locale
   * specific suffixes, then mapping non-ASCII digits into ASCII
   * digits via {@link Character#digit Character.digit}, prepending a
   * negative sign (-) if the locale specific negative prefixes and suffixes
   * were present, and passing the resulting string to
   * {@link Long#parseLong(String, int) Long.parseLong} with the
   * specified radix.
   *
   * @param radix the radix used to interpret the token as an int value
   * @return the <tt>long</tt> scanned from the input
   * @throws InputMismatchException if the next token does not match the <i>Integer</i> regular
   * expression, or is out of range
   * @throws NoSuchElementException if input is exhausted
   * @throws IllegalStateException if this scanner is closed
   */
  public long nextLong(int radix) {
    // Check cached result
    if ((typeCache != null) && (typeCache instanceof Long)
        && this.radix == radix) {
      long val = ((Long) typeCache).longValue();
      useTypeCache();
      return val;
    }
    setRadix(radix);
    clearCaches();
    try {
      String s = next(integerPattern());
      if (matcher.group(SIMPLE_GROUP_INDEX) == null) {
        s = processIntegerToken(s);
      }
      return Long.parseLong(s, radix);
    } catch (NumberFormatException nfe) {
      position = matcher.start(); // don't skip bad token
      throw new InputMismatchException(nfe.getMessage());
    }
  }

  /**
   * The float token must be stripped of prefixes, group separators,
   * and suffixes, non ascii digits must be converted into ascii digits
   * before parseFloat will accept it.
   *
   * If there are non-ascii digits in the token these digits must
   * be processed before the token is passed to parseFloat.
   */
  private String processFloatToken(String token) {
    String result = token.replaceAll(groupSeparator, "");
    if (!decimalSeparator.equals("\\.")) {
      result = result.replaceAll(decimalSeparator, ".");
    }
    boolean isNegative = false;
    int preLen = negativePrefix.length();
    if ((preLen > 0) && result.startsWith(negativePrefix)) {
      isNegative = true;
      result = result.substring(preLen);
    }
    int sufLen = negativeSuffix.length();
    if ((sufLen > 0) && result.endsWith(negativeSuffix)) {
      isNegative = true;
      result = result.substring(result.length() - sufLen,
          result.length());
    }
    if (result.equals(nanString)) {
      result = "NaN";
    }
    if (result.equals(infinityString)) {
      result = "Infinity";
    }
    if (isNegative) {
      result = "-" + result;
    }

    // Translate non-ASCII digits
    Matcher m = NON_ASCII_DIGIT.matcher(result);
    if (m.find()) {
      StringBuilder inASCII = new StringBuilder();
      for (int i = 0; i < result.length(); i++) {
        char nextChar = result.charAt(i);
        if (Character.isDigit(nextChar)) {
          int d = Character.digit(nextChar, 10);
          if (d != -1) {
            inASCII.append(d);
          } else {
            inASCII.append(nextChar);
          }
        } else {
          inASCII.append(nextChar);
        }
      }
      result = inASCII.toString();
    }

    return result;
  }

  /**
   * Returns true if the next token in this scanner's input can be
   * interpreted as a float value using the {@link #nextFloat}
   * method. The scanner does not advance past any input.
   *
   * @return true if and only if this scanner's next token is a valid float value
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNextFloat() {
    setRadix(10);
    boolean result = hasNext(floatPattern());
    if (result) { // Cache it
      try {
        String s = processFloatToken(hasNextResult);
        typeCache = Float.valueOf(Float.parseFloat(s));
      } catch (NumberFormatException nfe) {
        result = false;
      }
    }
    return result;
  }

  /**
   * Scans the next token of the input as a <tt>float</tt>.
   * This method will throw <code>InputMismatchException</code>
   * if the next token cannot be translated into a valid float value as
   * described below. If the translation is successful, the scanner advances
   * past the input that matched.
   *
   * <p> If the next token matches the <a
   * href="#Float-regex"><i>Float</i></a> regular expression defined above
   * then the token is converted into a <tt>float</tt> value as if by
   * removing all locale specific prefixes, group separators, and locale
   * specific suffixes, then mapping non-ASCII digits into ASCII
   * digits via {@link Character#digit Character.digit}, prepending a
   * negative sign (-) if the locale specific negative prefixes and suffixes
   * were present, and passing the resulting string to
   * {@link Float#parseFloat Float.parseFloat}. If the token matches
   * the localized NaN or infinity strings, then either "Nan" or "Infinity"
   * is passed to {@link Float#parseFloat(String) Float.parseFloat} as
   * appropriate.
   *
   * @return the <tt>float</tt> scanned from the input
   * @throws InputMismatchException if the next token does not match the <i>Float</i> regular
   * expression, or is out of range
   * @throws NoSuchElementException if input is exhausted
   * @throws IllegalStateException if this scanner is closed
   */
  public float nextFloat() {
    // Check cached result
    if ((typeCache != null) && (typeCache instanceof Float)) {
      float val = ((Float) typeCache).floatValue();
      useTypeCache();
      return val;
    }
    setRadix(10);
    clearCaches();
    try {
      return Float.parseFloat(processFloatToken(next(floatPattern())));
    } catch (NumberFormatException nfe) {
      position = matcher.start(); // don't skip bad token
      throw new InputMismatchException(nfe.getMessage());
    }
  }

  /**
   * Returns true if the next token in this scanner's input can be
   * interpreted as a double value using the {@link #nextDouble}
   * method. The scanner does not advance past any input.
   *
   * @return true if and only if this scanner's next token is a valid double value
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNextDouble() {
    setRadix(10);
    boolean result = hasNext(floatPattern());
    if (result) { // Cache it
      try {
        String s = processFloatToken(hasNextResult);
        typeCache = Double.valueOf(Double.parseDouble(s));
      } catch (NumberFormatException nfe) {
        result = false;
      }
    }
    return result;
  }

  /**
   * Scans the next token of the input as a <tt>double</tt>.
   * This method will throw <code>InputMismatchException</code>
   * if the next token cannot be translated into a valid double value.
   * If the translation is successful, the scanner advances past the input
   * that matched.
   *
   * <p> If the next token matches the <a
   * href="#Float-regex"><i>Float</i></a> regular expression defined above
   * then the token is converted into a <tt>double</tt> value as if by
   * removing all locale specific prefixes, group separators, and locale
   * specific suffixes, then mapping non-ASCII digits into ASCII
   * digits via {@link Character#digit Character.digit}, prepending a
   * negative sign (-) if the locale specific negative prefixes and suffixes
   * were present, and passing the resulting string to
   * {@link Double#parseDouble Double.parseDouble}. If the token matches
   * the localized NaN or infinity strings, then either "Nan" or "Infinity"
   * is passed to {@link Double#parseDouble(String) Double.parseDouble} as
   * appropriate.
   *
   * @return the <tt>double</tt> scanned from the input
   * @throws InputMismatchException if the next token does not match the <i>Float</i> regular
   * expression, or is out of range
   * @throws NoSuchElementException if the input is exhausted
   * @throws IllegalStateException if this scanner is closed
   */
  public double nextDouble() {
    // Check cached result
    if ((typeCache != null) && (typeCache instanceof Double)) {
      double val = ((Double) typeCache).doubleValue();
      useTypeCache();
      return val;
    }
    setRadix(10);
    clearCaches();
    // Search for next float
    try {
      return Double.parseDouble(processFloatToken(next(floatPattern())));
    } catch (NumberFormatException nfe) {
      position = matcher.start(); // don't skip bad token
      throw new InputMismatchException(nfe.getMessage());
    }
  }

  // Convenience methods for scanning multi precision numbers

  /**
   * Returns true if the next token in this scanner's input can be
   * interpreted as a <code>BigInteger</code> in the default radix using the
   * {@link #nextBigInteger} method. The scanner does not advance past any
   * input.
   *
   * @return true if and only if this scanner's next token is a valid <code>BigInteger</code>
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNextBigInteger() {
    return hasNextBigInteger(defaultRadix);
  }

  /**
   * Returns true if the next token in this scanner's input can be
   * interpreted as a <code>BigInteger</code> in the specified radix using
   * the {@link #nextBigInteger} method. The scanner does not advance past
   * any input.
   *
   * @param radix the radix used to interpret the token as an integer
   * @return true if and only if this scanner's next token is a valid <code>BigInteger</code>
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNextBigInteger(int radix) {
    setRadix(radix);
    boolean result = hasNext(integerPattern());
    if (result) { // Cache it
      try {
        String s = (matcher.group(SIMPLE_GROUP_INDEX) == null) ?
            processIntegerToken(hasNextResult) :
            hasNextResult;
        typeCache = new BigInteger(s, radix);
      } catch (NumberFormatException nfe) {
        result = false;
      }
    }
    return result;
  }

  /**
   * Scans the next token of the input as a {@link java.math.BigInteger
   * BigInteger}.
   *
   * <p> An invocation of this method of the form
   * <tt>nextBigInteger()</tt> behaves in exactly the same way as the
   * invocation <tt>nextBigInteger(radix)</tt>, where <code>radix</code>
   * is the default radix of this scanner.
   *
   * @return the <tt>BigInteger</tt> scanned from the input
   * @throws InputMismatchException if the next token does not match the <i>Integer</i> regular
   * expression, or is out of range
   * @throws NoSuchElementException if the input is exhausted
   * @throws IllegalStateException if this scanner is closed
   */
  public BigInteger nextBigInteger() {
    return nextBigInteger(defaultRadix);
  }

  /**
   * Scans the next token of the input as a {@link java.math.BigInteger
   * BigInteger}.
   *
   * <p> If the next token matches the <a
   * href="#Integer-regex"><i>Integer</i></a> regular expression defined
   * above then the token is converted into a <tt>BigInteger</tt> value as if
   * by removing all group separators, mapping non-ASCII digits into ASCII
   * digits via the {@link Character#digit Character.digit}, and passing the
   * resulting string to the {@link
   * java.math.BigInteger#BigInteger(java.lang.String)
   * BigInteger(String, int)} constructor with the specified radix.
   *
   * @param radix the radix used to interpret the token
   * @return the <tt>BigInteger</tt> scanned from the input
   * @throws InputMismatchException if the next token does not match the <i>Integer</i> regular
   * expression, or is out of range
   * @throws NoSuchElementException if the input is exhausted
   * @throws IllegalStateException if this scanner is closed
   */
  public BigInteger nextBigInteger(int radix) {
    // Check cached result
    if ((typeCache != null) && (typeCache instanceof BigInteger)
        && this.radix == radix) {
      BigInteger val = (BigInteger) typeCache;
      useTypeCache();
      return val;
    }
    setRadix(radix);
    clearCaches();
    // Search for next int
    try {
      String s = next(integerPattern());
      if (matcher.group(SIMPLE_GROUP_INDEX) == null) {
        s = processIntegerToken(s);
      }
      return new BigInteger(s, radix);
    } catch (NumberFormatException nfe) {
      position = matcher.start(); // don't skip bad token
      throw new InputMismatchException(nfe.getMessage());
    }
  }

  /**
   * Returns true if the next token in this scanner's input can be
   * interpreted as a <code>BigDecimal</code> using the
   * {@link #nextBigDecimal} method. The scanner does not advance past any
   * input.
   *
   * @return true if and only if this scanner's next token is a valid <code>BigDecimal</code>
   * @throws IllegalStateException if this scanner is closed
   */
  public boolean hasNextBigDecimal() {
    setRadix(10);
    boolean result = hasNext(decimalPattern());
    if (result) { // Cache it
      try {
        String s = processFloatToken(hasNextResult);
        typeCache = new BigDecimal(s);
      } catch (NumberFormatException nfe) {
        result = false;
      }
    }
    return result;
  }

  /**
   * Scans the next token of the input as a {@link java.math.BigDecimal
   * BigDecimal}.
   *
   * <p> If the next token matches the <a
   * href="#Decimal-regex"><i>Decimal</i></a> regular expression defined
   * above then the token is converted into a <tt>BigDecimal</tt> value as if
   * by removing all group separators, mapping non-ASCII digits into ASCII
   * digits via the {@link Character#digit Character.digit}, and passing the
   * resulting string to the {@link
   * java.math.BigDecimal#BigDecimal(java.lang.String) BigDecimal(String)}
   * constructor.
   *
   * @return the <tt>BigDecimal</tt> scanned from the input
   * @throws InputMismatchException if the next token does not match the <i>Decimal</i> regular
   * expression, or is out of range
   * @throws NoSuchElementException if the input is exhausted
   * @throws IllegalStateException if this scanner is closed
   */
  public BigDecimal nextBigDecimal() {
    // Check cached result
    if ((typeCache != null) && (typeCache instanceof BigDecimal)) {
      BigDecimal val = (BigDecimal) typeCache;
      useTypeCache();
      return val;
    }
    setRadix(10);
    clearCaches();
    // Search for next float
    try {
      String s = processFloatToken(next(decimalPattern()));
      return new BigDecimal(s);
    } catch (NumberFormatException nfe) {
      position = matcher.start(); // don't skip bad token
      throw new InputMismatchException(nfe.getMessage());
    }
  }

  /**
   * Resets this scanner.
   *
   * <p> Resetting a scanner discards all of its explicit state
   * information which may have been changed by invocations of {@link
   * #useDelimiter}, {@link #useLocale}, or {@link #useRadix}.
   *
   * <p> An invocation of this method of the form
   * <tt>scanner.reset()</tt> behaves in exactly the same way as the
   * invocation
   *
   * <blockquote><pre>{@code
   *   scanner.useDelimiter("\\p{javaWhitespace}+")
   *          .useLocale(Locale.getDefault(Locale.Category.FORMAT))
   *          .useRadix(10);
   * }</pre></blockquote>
   *
   * @return this scanner
   * @since 1.6
   */
  public Scanner reset() {
    delimPattern = WHITESPACE_PATTERN;
    useLocale(Locale.getDefault(Locale.Category.FORMAT));
    useRadix(10);
    clearCaches();
    return this;
  }
}
